Statement I : ADA deficiency disorder is caused due to the excessive synthesis of gene for adenosine deaminase.

Statement II :It affects the human immune system.

Only statement II is correct .

Statement I is incorrect. ADA deficiency disorder is not caused by excessive synthesis of the gene for adenosine deaminase. Instead, ADA deficiency disorder, also known as Severe Combined Immunodeficiency (SCID), is caused by a genetic mutation that leads to a deficiency or absence of the adenosine deaminase enzyme. This enzyme is crucial for the normal development and functioning of the immune system. ADA deficiency disorder is caused by a mutation in the gene that codes for adenosine deaminase (ADA). This mutation results in a lack of ADA enzyme, which is needed to break down adenosine and deoxyadenosine. The accumulation of these molecules in the body damages the immune system and leads to a variety of health problems.

Statement II is correct. It is correct that ADA deficiency disorder affects the human immune system. Individuals with ADA deficiency have a severely compromised immune system, making them highly susceptible to severe and life-threatening infections. Without functional ADA enzyme, toxic metabolic byproducts accumulate in the immune cells, particularly lymphocytes, leading to their dysfunction and reduced ability to fight infections .Without treatment, most people with SCID die before the age of 2.

So the correct answer is Statement II only.